it is very nearly impossible to advise specifically on such a question without considerable knowledge of the circumstances. However, if you have staff committed to out of hours support, then why not train them to conduct incident management on their own? That should not be difficult since they will only have to perform a subset of full incident management and hand over the next morning. Meanwhile they should have resolved the incident if that was possible. It is mostly about giving them authority to act in defined circumstances._________________"Method goes far to prevent trouble in business: for it makes the task easy, hinders confusion, saves abundance of time, and instructs those that have business depending, both what to do and what to hope."
William Penn 1644-1718